Description

This study aims to determine how concrete structures used in waste management scenarios have aged, and any effects on the structural properties. Particular focus is given to the effects of carbonation and gamma radiation, which are investigated through changes in the compressive strength, pore water chemistry, and microstructure. These two degradation mechanisms will be investigated individually as well as simultaneously.

Concrete is used throughout the nuclear industry, in both a radiation shielding role as well as a building material. Previous research conducted into the radiation tolerance of concrete has predominantly focussed on conditions representative of a nuclear reactor, such as neutron or neutron-gamma irradiation. Consequently, only a small proportion of papers have examined the sole effects of gamma radiation on concrete, a situation applicable to waste management structures. Furthermore, the majority of concrete structures present across the U.K. civil nuclear estate are over 20 years old. The vitrified product store is such a structure, housing high level waste incorporated into a glass matrix and stored inside stainless steel canisters. As a result, the store is exposed to elevated temperatures, gamma radiation and potentially carbonation.

Conditions representative of the vitrified product store’s lifetime will be simulated using an accelerated carbonation chamber and an elevated gamma dose rate. Fresh samples are batch produced to replicate the specification of the concrete used for the vitrified product store. A comparison will be made to historic samples recovered from the structure upon construction, some of which have been inside the store accumulating a dose for over 20 years.